Electronic pen and coordinate input apparatus

ABSTRACT

Disclosed is an electronic pen that includes a conductive core body, a power supply circuit, a first signal generation circuit which receives power from the power supply circuit and generates a first signal, and a second signal generation circuit which receives power from the power supply circuit and generates a second signal different from the first signal, and an operation switch which sets an operation mode of the electronic pen to either a first operation mode or a second operation mode. While the operation mode of the electronic pen is set to the first operation mode, the conductive core body transmits the first signal generated by the first signal generation circuit. While the operation mode of the electronic pen is set to the second operation mode, the conductive core body transmits the second signal generated by the second signal generation circuit.

BACKGROUND Technical Field

The present disclosure relates to an electronic pen of the so-calledactive capacitive coupling system that is used in conjunction with atablet and transmits signals to the tablet. The disclosure also relatesto a coordinate input apparatus made up of a tablet and an activecapacitive coupling type of electronic pen.

2. Description of the Related Art

Diverse types of electronic pens (stylus pen) for use with tablets havebeen proposed, including an electronic induction type of electronic penand a capacitive coupling type of electronic pen. Of these types ofelectronic pens, ones operating by active capacitive coupling haverecently appeared. The active capacitive coupling type of electronic penincorporates a power supply part that uses a primary or a secondarybattery and a signal transmission part. This electronic pen further hasa core body formed by a conductor and outputs via the conductive corebody a signal coming from the signal transmission part to the tablet bycapacitive coupling (e.g., see Patent Literature 1 “Japanese Patent No.5687398”).

The signal output from the active capacitive coupling type of electronicpen has a large amplitude of 15 volts or more, for example. This allowsthe tablet to detect with high resolution the position indicated by theelectronic pen.

The active capacitive coupling type of electronic pen uses the primarybattery or a rechargeable secondary battery as its power supply, andthere may be diverse waveforms in which the signal is transmitted by theelectronic pen. Typically, the waveforms may be sine waves andrectangular waves. In the case of an electronic pen that uses a sinewave signal as its transmission signal, a resonance capacitor of aninternal resonance circuit absorbs the effects of stray capacitance.This minimizes power loss and prolongs battery life. However, the use ofa transformer is preferred, which incurs the disadvantage of making thecircuit configuration relatively complicated.

Meanwhile, in the case of an electronic pen that uses a rectangular wavesignal as its transmission signal, there is an advantage of a signalgeneration circuit being configured simply as long as a digital signalsupplied from the electronic pen to the tablet is a binary signal. Thedisadvantage, on the other hand, is an increasing power loss caused bystray capacitance leading to shorter battery life. Incidentally, inorder to generate the rectangular wave signal of a large amplitude fromthe battery voltage with the simplified configuration, there may be useda circuit that includes a transformer for boosting purposes.

As described above, there are advantages and disadvantages as to whichof the sine wave signal and the rectangular wave signal is to be used asthe signal transmitted from the active capacitive coupling type ofelectronic pen. As a result, what is expected is the marketing andcoexistence of the two types of active capacitive coupling type ofelectronic pens: one using the sine wave signal as the transmissionsignal and the other using the rectangular wave signal as thetransmission signal. What is also expected is the coexistence of twotypes of tablets: one that receives the sine wave signal from theelectronic pen for position detection and other signal processing, andthe other that receives the rectangular wave signal from the electronicpen also for position detection and other signal processing.

Given the circumstances, users have to change electronic pens dependingon tablet type, i.e., whether the tablet receives the sine wave signalor the rectangular wave signal from the electronic pen. The changing ofthe electronic pens is troublesome and economically inefficient.

BRIEF SUMMARY

An object of the present disclosure is to provide an electronic pen thatsolves the above problems.

In solving the above problems, there is provided an electronic penincluding: a conductive core-side member; a power supply circuit; asignal transmission circuit which, in operation, receives a power supplyvoltage from the power supply circuit, generates a first signal and asecond signal each having a different waveform, and selectively supplieseither the first signal or the second signal to the core-side member; aninput reception which, in operation, receives a designation inputdesignating either the first signal or the second signal to be suppliedfrom the signal transmission circuit to the core-side member; and acontrol which, in operation, controls the signal transmission circuit tosupply either the first signal or the second signal to the core-sidemember according to the designation input received by the inputreception circuit.

The electronic pen of the above-described configuration supports both atablet adapted to the first signal and a tablet adapted to the secondsignal. The electronic pen thus provides a significant advantage ofbeing both convenient and economical because there is no need to preparean electronic pen for each tablet and because the electronic pen can beshared with the different tablets.

Preferably, the signal transmission circuit may include a sine wavesignal generation which, in operation, generates a sine wave signal asthe first signal. The sine wave signal generation circuit may include atransformer of which the primary winding side is connected with acapacitor to constitute a resonance circuit, the secondary winding sideof the transformer outputting the sine wave signal. The secondarywinding side of the transformer may have a rectifier circuit of whichthe output voltage is used as the power supply voltage for the signalgeneration circuit that generates the second signal.

The electronic pen of the preferred configuration described abovesupports both a tablet adapted to the sine wave signal as the firstsignal and a tablet adapted to the second signal of a differentwaveform. The sine wave signal generation circuit generating the sinewave signal has the transformer of which the primary winding side isconnected with the capacitor to constitute the resonance circuit, thesecondary winding side of the transformer outputting the sine wavesignal. The sine wave signal generation circuit thus generates the sinewave signal boosted by the transformer. Also, the rectifier circuitprovided on the secondary winding side of the transformer generates thepower supply voltage for the signal generation circuit that generatesthe second signal. The electronic pen thus provides a significantadvantage of a simplified configuration furnished with only onetransformer because there is no need to prepare a dedicated transformerto generate a high supply voltage for the signal generation circuit forgenerating the second signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram explaining an outline of a coordinateinput apparatus in a first embodiment of the present disclosure;

FIG. 2 is a block diagram depicting an example of an electricalconfiguration of an electronic pen in the first embodiment of thepresent disclosure;

FIG. 3 is an explanatory diagram explaining a sine wave mode of theelectronic pen in the first embodiment of the present disclosure;

FIG. 4 is an explanatory diagram explaining the sine wave mode of theelectronic pen in the first embodiment of the present disclosure;

FIG. 5 is an explanatory diagram explaining a rectangular wave mode ofthe electronic pen in the first embodiment of the present disclosure;

FIG. 6 is another explanatory diagram explaining the rectangular wavemode of the electronic pen in the first embodiment of the presentdisclosure;

FIG. 7 is an explanatory diagram explaining the rectangular wave mode ofthe electronic pen in the first embodiment of the present disclosure;

FIG. 8 is a flowchart explaining the flow of a mode switching controlprocess of the electronic pen in the first embodiment of the presentdisclosure;

FIG. 9 is a schematic diagram explaining an example of an electricalconfiguration of a sine wave type tablet of the coordinate inputapparatus in the first embodiment of the present disclosure;

FIG. 10 is a schematic diagram explaining a transmission signal of theelectronic pen in the sine wave mode in the first embodiment of thepresent disclosure;

FIG. 11 is a schematic diagram explaining an outline of a coordinateinput apparatus in a second embodiment of the present disclosure;

FIG. 12 is a block diagram depicting an example of an electricalconfiguration of an electronic pen in the second embodiment of thepresent disclosure;

FIG. 13 is a flowchart explaining a flow of a mode switching controlprocess of the electronic pen in the second embodiment of the presentdisclosure;

FIG. 14 is another flowchart explaining the flow of the mode switchingcontrol process of the electronic pen in the second embodiment of thepresent disclosure;

FIG. 15 is a schematic diagram explaining an example of an electricalconfiguration of a sine wave type tablet of the coordinate inputapparatus in the second embodiment of the present disclosure;

FIG. 16 is a block diagram depicting an example of an electricalconfiguration of an electronic pen in a third embodiment of the presentdisclosure;

FIG. 17 is a schematic diagram explaining outlines of an electronic penand a tablet constituting a coordinate input apparatus in a fourthembodiment of the present disclosure;

FIG. 18 is a block diagram depicting an example of an electricalconfiguration of an electronic pen in a fifth embodiment of the presentdisclosure;

FIG. 19 is an explanatory diagram explaining the rectangular wave modeof the electronic pen in the fifth embodiment of the present disclosure;and

FIG. 20 is an explanatory diagram explaining the rectangular wave modeof the electronic pen in the fifth embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

Described below are an electronic pen and a coordinate input apparatusin a first embodiment of the present disclosure. First of all, outlinesof the electronic pen and the coordinate input apparatus in the firstembodiment of the disclosure are explained with reference to FIG. 1. Forthe first embodiment to be described below, it is assumed that a firstsignal and a second signal of different waveforms are output from theelectronic pen 1 and that the first signal is a sine wave signal and thesecond signal is a rectangular wave signal.

For the embodiment to be described below, it is also assumed that thesine wave signal as the first signal and the rectangular wave signal asthe second signal are different from each other not only in waveform butalso in frequency and in amplitude. For example, the sine wave signalhas a frequency of 1.8 MHz and an amplitude of 17 volts; the rectangularwave signal has a frequency of tens of kHz and an amplitude of 20 volts.In the electronic pen 1 of the first embodiment, a conductive core 11 isprovided as a core-side member through which signals are exchanged witha tablet.

The electronic pen 1 of this embodiment, together with the tablet,constitutes the coordinate input apparatus. In this embodiment, asdepicted in FIG. 1, there are two types of tablets: a first type oftablet 2S (called a sine wave type of tablet hereunder) that receives asine wave signal Ss sent from the electronic pen 1 to detect theposition indicated by the electronic pen 1, and a second type of tablet2R (called a rectangular wave type of tablet hereunder) that receives arectangular signal Sr transmitted from the electronic 1 to detect theposition indicated by the electronic pen 1.

Also, the electronic pen 1 of this embodiment is configured to have asine wave mode in which the sine wave signal Ss is generated as thetransmission signal and a rectangular wave mode in which the rectangularwave signal Sr is generated as the transmission signal, the two modesbeing switched depending on the tablet 2S or the tablet 2R being in use.

In this embodiment, the tablets 2S and 2R have housings 20S and 20R thatrespectively accommodate position detection sensors 21S and 21Rexchanging signals with the electronic pen 1 by capacitive coupling.Also provided are pen indication detection circuits 22S and 22R that areconnected respectively with the position detection sensors 21S and 21Rand perform signal processing.

In this case, the position detection sensors 21S and 21R have the sameconfiguration. However, the pen indication detection circuits 22S and22R are different from each other in configuration. That is, the penindication detection circuit 22S is configured to receive the sine wavesignal Ss from the electronic pen 1 to perform a position detectionprocess and other processes, and the pen indication detection circuit22R is configured to receive the rectangular wave signal Sr from theelectronic pen 1 to carry out the position detection process and otherprocesses.

The electronic pen 1 of this embodiment has a slide operation switch 30as an example of a mode switching operation section. The slide operationswitch 30 constitutes an input reception circuit. In this example, asdepicted in FIG. 1, the slide operation switch 30 has a character “S”printed or engraved, for example, at one end of an elongated hole 31 inthe axial direction of a housing 10 and a character “R” printed orengraved, for example, at the other end of the elongated hole 31.

When a slide operation button 32 of the slide operation switch 30 inthis example is at the “S” end of the elongated hole 31, a low-levelstate indicative of the sine wave mode is brought about, for example.When the slide operation button 32 is at the “R” end of the elongatedhole 31, a mode designation signal SE (see FIG. 2, to be discussedlater) producing a high-level state indicative of the rectangular wavemode is generated, for example.

The user performs a switching operation of the slide operation switch 30in a manner depending on whether the tablet in use is the sine wave typeof tablet 2S or the rectangular wave type of tablet 2R. The electronicpen 1 is then brought into the mode reflecting the switching operation,outputting either the sine wave signal Ss or the rectangular wave signalSr via the core 11. Incidentally, the electronic pen 1 may output thesine wave signal Ss or the rectangular wave signal Sr via a cone-shapedcover 10C covering the core 11.

The tablet 2S or 2R receives, depending on its type, either the sinewave signal Ss or the rectangular wave signal Sr from the electronic pen1. Given the signal, the tablet 2S or 2R proceeds to perform theprocesses of detecting the position indicated by the electronic pen,detecting writing pressure information, and detecting identificationinformation identifying the electronic pen 1, and to process otheradditional information.

In the manner described above, the electronic pen 1 of this embodimentcan be used to indicate positions on both the tablet 2S and the tablet2R.

Incidentally, the mode switching operation section is not limitedstructurally to the slide operation switch 30. Alternatively, the modeswitching operation section may be a seesaw type selector switch, or apair of pushbutton switches representing the sine wave mode and therectangular wave mode, for example. As another alternative, switchingmay be performed between the sine wave mode and the rectangular wavemode every time one pushbutton switch is pressed. As a furtheralternative, a signal output from the tablet 2S or 2R may be used toswitch between the sine wave mode and the rectangular wave mode. Exampleof an electrical configuration of the electronic pen 1

The electronic pen 1 of this embodiment is configured simply to generatesignals of the above-mentioned two different waveforms. Thus, onefeature of the electronic pen 1 of this embodiment is that the simplyconfigured electronic pen 1 outputs signals of two different waveformswithout becoming larger in size.

FIG. 2 depicts a representative signal processing circuit as an exampleof an electrical configuration of the electronic pen 1 in the firstembodiment. The electronic pen 1 of this embodiment includes theconductive core 11 through which to transmit the sine wave signal Ss orthe rectangular wave signal Sr. The core 11 is configured with aconductive metal, for example.

Also, the electronic pen 1 of this embodiment has a power supply voltageVDD generated by a power supply circuit 12 that includes a primary or asecondary battery. For example, a lithium ion battery is used as thesecondary battery. The power supply circuit 12 may be configured with anelectrical storage element such as an electric double layer capacitor ora lithium ion capacitor in place of, or in combination with thesecondary battery. The power supply circuit 12 may alternatively beconfigured with an autonomous power generation element such as a solarcell, as well as the electrical storage element such as an electricdouble layer capacitor or a lithium ion capacitor.

The signal processing circuit of the electronic pen 1 in this embodimentis configured with an integrated circuit (IC) 100 and its externalcomponents. The IC 100 has terminals 101 to 109. The power supplyvoltage VDD from the power supply circuit 12 is supplied to the IC 100via the terminal 101.

The signal processing circuit configured with the IC 100 and itsexternal components includes a transmission information generationcircuit 110, a sine wave signal generation circuit 120 that generatesthe sine wave signal Ss as the typical first signal, a rectangular wavesignal generation circuit 130 that generates the rectangular wave signalSr as the typical second signal, a control circuit 140, a mode switchingcircuit 150, and a rectifier circuit 17.

The mode switching circuit 150 includes a sine wave mode terminal Ts, arectangular wave mode terminal Tr, and a common terminal Cm. A modeswitching signal SW from a mode switching signal generation circuit 141,to be discussed later, in the control circuit 140 causes the modeswitching circuit 150 to connect the common terminal Cm with either thesine wave mode terminal Ts or the rectangular wave mode terminal Tr.

The common terminal Cm of the mode switching circuit 150 is connectedwith the conductive core 11 of the electronic pen 1 via the terminal 102of the IC 100. The mode switching circuit 150 is configured to have itssine wave mode terminal Ts supplied with the sine wave signal Ss fromthe sine wave signal generation circuit 120 via the terminal 103 of theIC 100. The mode switching circuit 150 is also configured to have itsrectangular wave mode terminal Tr supplied with the rectangular wavesignal Sr from the rectangular wave signal generation circuit 130.

The control circuit 140 in this embodiment is configured with a modeswitching signal generation circuit 141, a sine wave control signalgeneration circuit 142, a rectangular wave control signal generationcircuit 143, and a selector switch circuit 144.

The mode switching signal generation circuit 141 receives input of themode designation signal SE from the slide operation switch 30 via theterminal 109 of the IC 100. On the basis of the input mode designationsignal SE, the mode switching signal generation circuit 141 determineswhether the sine wave mode or the rectangular wave mode is to beselected as the transmission mode of the electronic pen 1. In accordancewith the result of the determination, the mode switching signalgeneration circuit 141 generates the mode switching signal SW. The modeswitching signal generation circuit 141 then supplies the generated modeswitching signal SW to the transmission information generation circuit110, to a selector switch circuit 122, to be discussed later, of thesine wave signal generation circuit 120, to the selector switch circuit144 of the control circuit 140, and to the mode switching circuit 150.

Receiving the mode switching signal SW from the mode switching signalgeneration circuit 141, the transmission information generation circuit110 generates transmission information to be sent to the tablet 2S or2R. In accordance with the mode switching signal SW, the signalcorresponding to the transmission information generated by thetransmission information generation circuit 110 is controlled to differbetween the sine wave mode and the rectangular wave mode. However, thecontent of the transmission information is the same for both the sinewave mode and the rectangular wave mode.

In the sine wave mode, the transmission information generation circuit110 supplies the signal for the sine wave mode to the sine wave controlsignal generation circuit 142 in the control circuit 140. In therectangular wave mode, the transmission information generation circuit110 supplies the signal for the rectangular wave mode to the rectangularwave signal generation circuit 130.

The transmission information includes, in addition to the signal forposition detection, information signals that represent informationregarding the writing pressure detected by a writing pressure detectionmechanism (not illustrated) included in the electronic pen 1, on-offinformation regarding a side switch (not illustrated) attached to theelectronic pen 1, and identification information stored in a memory (notillustrated) to identify the electronic pen 1.

The sine wave signal generation circuit 120 is configured with atransformer 13, a resonance capacitor 14, a bias generation capacitor15, and a backflow prevention diode 16 as external components, as wellas a switch circuit 121 and the selector switch circuit 122 inside theIC 100. In the electronic pen 1 of this embodiment, the transformer 13is used not only to generate the sine wave signal but also to produce ahigh power supply voltage for generating the rectangular wave signal.

As described above, the signal output from the electronic pen 1 of thisembodiment to the tablet 2S or 2R is a large-amplitude signal of 17 or20 volts, for example. On the other hand, the power supply voltage VDDfrom the power supply circuit 12 that uses the primary or the secondarybattery is a low voltage. For this reason, the transformer 13 is usednot only to generate the sine wave signal Ss but also to perform theprocess of boosting the sine wave signal Ss for larger amplitude.

Because the rectangular wave signal Sr is also a large-amplitude signal,it is necessary to generate a high voltage from the power supply voltageVDD, and accordingly, the boosting is generally accomplished using atransformer. However, if the transformer 13 for generating the sine wavesignal and for boosting the voltage is supplemented with a separatetransformer for generating the high voltage for the rectangular wavesignal, that means two transformers coexist in the electronic pen 1.This can increase the size of the electronic pen 1, making it difficultto manufacture a slender electronic pen 1. In order to solve thisproblem, the first embodiment is configured to use the transformer 13not only to generate the sine wave signal but also to produce the highvoltage for generating the rectangular wave signal.

The transformer 13 has a primary winding 13 a and a secondary winding 13b. A turn ratio of the primary winding 13 a to the secondary winding 13b is 1:n (n>1 where n=5, for example). One end of the primary winding 13a of the transformer 13 is connected with one end of the resonancecapacitor 14 that constitutes, together with the primary winding 13 a, aresonance circuit. The one end of the primary winding 13 a is alsoconnected with the terminal 105 of the IC 100 where the power supplyvoltage VDD is obtained. The other end of the primary winding 13 a ofthe transformer 13 is connected, via the terminal 107, with one end ofthe switch circuit 121 and with a connection point P1 for the otherswitching terminal b of the selector switch circuit 122.

The other end of the resonance capacitor 14 is connected with a commonterminal c of the selector switch circuit 122 via the terminal 106 ofthe IC 100. One switching terminal a of the selector switch circuit 122is connected with the terminal 101 where the power supply voltage VDD isobtained. The other switching terminal b of the selector switch circuit122 is connected with one end of the switch circuit 121. The other endof the selector switch circuit 121 is connected with the terminal 108that is grounded.

In this embodiment, an oscillation circuit 120R is configured with aresonance circuit formed by the primary winding 13 a of the transformer13 and by the resonance capacitor 14 and with a circuit that includesthe switch circuit 121. In the sine wave mode, the oscillation circuit120R performs an oscillation operation using the resonance circuit madeup of the primary winding 13 a of the transformer 13 and the resonancecapacitor 14. At an appropriate timing, the switch circuit 121 iscontrolled to be turned on and off to energize the oscillation circuit120R. This makes it possible to continue the oscillation of theoscillation circuit 120R without attenuating its oscillation outputsignal (i.e., sine wave signal).

Also in this embodiment, the switch circuit 121 in the rectangular wavemode is controlled to be turned on and off to generate a power supplyvoltage (high voltage HV (=HVr)) corresponding to the amplitude of therectangular wave signal to be generated, using the transformer 13 as aflyback type step-up transformer. That is, in this embodiment, not onlythe transformer 13 but also the switch circuit 121 is used in both thesine wave mode and the rectangular wave mode.

It is to be noted, however, that the switch circuit in this embodimentis controlled to be turned on and off differently between the sine wavemode and the rectangular wave mode. Thus, as depicted in FIG. 2, theselector switch circuit 144 is provided along with the sine wave controlsignal generation circuit 142 and the rectangular wave control signalgeneration circuit 143 so as to partially make up the control circuit140.

The selector switch circuit 122 is provided to switch between two typesof configurations. In the sine wave mode, the selector switch circuit122 connects the resonance capacitor 14 in parallel with the primarywinding 13 a of the transformer 13 to configure the resonance circuit.In the rectangular wave mode, the selector switch circuit 122disconnects the parallel connection between the resonance capacitor 14and the primary winding 13 a of the transformer 13 so as not toconfigure the resonance circuit. The mode switching signal SW from themode switching signal generation circuit 141 causes the selector switchcircuit 122 to connect the common terminal c with the switching terminalb in the sine wave mode, and connect the common terminal c with theswitching terminal a in the rectangular wave mode.

By monitoring the voltage VC obtained at the connection point P1, thesine wave control signal generation circuit 142 generates a sine wavecontrol signal to turn on and off the switch circuit 121 causing theoscillation circuit 120R to generate the sine wave signal Ss. Therectangular wave control signal generation circuit 143 generates arectangular wave control signal to turn on and off the switch circuit121 causing the rectifier circuit 17 to produce a high voltage HV (HVr)necessary for generating the rectangular wave signal Sr.

The switch circuit 121 is configured to be selectively supplied, via theselector switch circuit 144, with the sine wave control signal from thesine wave control signal generation circuit 142 and with the rectangularwave control signal from the rectangular wave control signal generationcircuit 143.

The mode switching signal SW from the mode switching signal generationcircuit 141 switches the selector switch circuit 144 to the side of thesine wave control signal generation circuit 142 in the sine wave mode orto the side of the rectangular wave control signal generation circuit143 in the rectangular wave mode. Processing operations performed by thesine wave control signal generation circuit 142 and by the rectangularwave control signal generation circuit 143 will be discussed later indetail.

One end of the secondary winding 13 b of the transformer 13 is connectedwith the cathode of the diode 16 for bias generation. The anode of thediode 16 is both grounded and connected with the terminal 108 of the IC100. The other end of the secondary winding 13 b of the transformer 13is both grounded via the bias generation capacitor 15 and connected withthe terminal 108 of the IC 100.

A connection point P2 between the one end of the secondary winding 13 bof the transformer 13 and the cathode of the diode 16 is connected withthe terminal 103 of the IC 100. A signal obtained at the connectionpoint P2 is supplied into the IC 100 via the terminal 103. The signalbrought into the IC 100 via the terminal 103 is supplied to the sinewave mode terminal Ts of the mode switching circuit 150.

The connection point P2 is also connected with the rectifier circuit 17formed by a rectifier diode 18 and a capacitor 19. An output terminal ofthe rectifier circuit 17 is connected with the terminal 104 of the IC100. The rectifier circuit 17 rectifies the signal obtained at theconnection point P2 at the one end of the secondary winding 13 b of thetransformer 13, thereby generating the high voltage HV boosted inaccordance with the turn ratio of the primary winding 13 a to thesecondary winding 13 b in the transformer 13.

That is, in the sine wave mode, the rectifier circuit 17 rectifies thesine wave signal Ss obtained at the connection point P2 at the one endof the secondary winding 13 b of the transformer 13, thereby generatingthe high voltage HV (=HVs) corresponding to the amplitude of this sinewave signal Ss. The high voltage HV (=HVs) in the sine wave mode is usedas the power supply voltage for the mode switching circuit 150.

In the rectangular wave mode, the rectifier circuit 17 rectifies, by theflyback method to be discussed later, the signal obtained at theconnection point P2 at the one end of the secondary winding 13 b, thusgenerating the high voltage HV (=HVr) necessary for generating therectangular wave signal Sr. The high voltage HV (=HVr) in therectangular wave mode is used as the power supply voltage for both therectangular wave signal generation circuit 130 and the mode switchingcircuit 150.

The rectangular wave signal generation circuit 130 in this embodiment isconfigured with a level conversion circuit 131 for rectangular wavesignal generation. The power supply voltage for the level conversioncircuit 131 is the high voltage HV (HVr) generated by the rectifiercircuit 17. The rectangular wave signal generation circuit 130 will bediscussed later in detail.

Described below are the processing operations performed by the sine wavecontrol signal generation circuit 142 in the mode for sine wave signalgeneration and by the rectangular wave control signal generation circuit143 in the rectangular wave mode in the signal processing circuit of theelectronic pen 1 configured as described above.

Processing Operations by the Sine Wave Control Signal Generation Circuit142

FIG. 3 is an explanatory diagram explaining a specific circuit exampleof the sine wave control signal generation circuit 142 as well as theprocessing operations performed by the sine wave control signalgeneration circuit 142 in the sine wave mode. FIG. 4 is anotherexplanatory diagram explaining the processing operations carried out bythe sine wave control signal generation circuit 142.

In the circuit example of FIG. 3, the switch circuit 121 is configuredwith one field-effect transistor (FET). In the illustration, theselector switch circuit 122 is in a switching state for the sine wavemode, with the common terminal c set to the switching terminal b toconstitute the oscillation circuit 120R that includes an LC resonancecircuit formed by the primary winding 13 a of the transformer 13 and bythe resonance capacitor 14. Note that, in FIG. 3, the switch circuit 144is omitted for the purpose of simplification.

The sine wave control signal generation circuit 142 of this exampleincludes a zero-cross detection circuit 1421, a delay circuit 1422, anda pulse generation circuit 1423.

The oscillation circuit 120R including the LC resonance circuit made upof the primary winding 13 a of the transformer 13 and the resonancecapacitor 14 causes a sine wave voltage VC to be obtained at theconnection point P1, the sine wave voltage VC having a frequency of 1.8MHz and an amplitude of 2VDD for example, as illustrated in the upperportion of FIG. 4. The sine wave voltage VC obtained at the connectionpoint P1 is used as an input signal to the zero-cross detection circuit1421.

The zero-cross detection circuit 1421 detects zero-cross points of thesine wave voltage VC behaving as a sine wave, i.e., time points Zc1 andZc2 (see upper portion of FIG. 4) at which the sine wave voltage VCcrosses the voltage value VDD. Given the detected zero-cross points Zc1and Zc2, the zero-cross detection circuit 1421 supplies the delaycircuit 1422 with the zero-cross point Zc2 at which the transitionoccurs from high to low voltage in the form of a signal such as a pulseindicative of the point Zc2.

Base on the signal from the zero-cross detection circuit 1421, the delaycircuit 1422 supplies the pulse generation circuit 1423 with a signalsuch as a pulse signal indicative of a time point delayed from thezero-cross point Zc2 by a delay time DL corresponding to ¼ of one cycleT of the sine wave voltage VC. Based on the signal from the delaycircuit 1422, the pulse generation circuit 1423 generates a switchingsignal SWs of a predetermined pulse width (see lower portion of FIG. 4).The pulse width of the switching signal SWs is short. The switchingsignal SWs from the pulse generation circuit 1423 is supplied to theswitch circuit 121 via the selector switch circuit 144, not illustratedin FIG. 3. The switch circuit 121 is turned on during the pulse widthperiod of the switching signal SWs. In the sine wave mode, the switchingcircuit 121 is turned off during periods other than the pulse widthperiod of the switching signal SWs.

When the switch circuit 121 is turned on during the pulse width periodof the switching signal SWs, a current flows through the switch circuit121 to the resonance circuit formed by the primary winding 13 a of thetransformer 13 and by the resonance capacitor 14. The sine wave voltageVC is thus generated continuously by the oscillation circuit 120Rwithout being attenuated.

It is to be noted here that the delay time DL of the delay circuit 1422corresponds to ¼ of one cycle T of the sine wave voltage VC past thezero-cross point Zc2. Thus, as seen in the lower portion of FIG. 4, theswitch circuit 121 is turned on at the time point at which the sine wavevoltage VC reaches zero volts. That means the voltage loss uponswitching of the switch circuit 121 is approximately zero.

On the side of the secondary winding 13 b of the transformer 13 appearsthe sine wave signal (sine wave voltage) Ss that is n times the sinewave voltage VC according to the turn ratio of 1:n between the primarywinding 13 a and the secondary winding 13 b is obtained.

The sine wave signal Ss is supplied to the rectifier circuit 17 as wellas to the mode switching circuit 150 via the terminal 103 of the IC 100.The rectifier circuit 17 rectifies the sine wave signal Ss to generatethe high voltage HV (=HVs). The high voltage (=HVs) generated by therectifier circuit 17 is supplied as the power supply voltage to the modeswitching circuit 150, not depicted in the example of FIG. 3, via theterminal 104 of the IC 100.

The signal from the transmission information generation circuit 110 issupplied as an enable signal to the sine wave control signal generationcircuit 142, which puts the sine wave signal generation circuit 120under enable control. That is, a digital signal of information (see FIG.5, to be discussed later) sent from the transmission informationgeneration circuit 110 enables the sine wave signal generation circuit120 while the signal is being “1” and disables the sine wave signalgeneration circuit 120 while the signal is being “0,” for example. As aresult, the sine wave signal Ss obtained on the side of the secondarywinding 13 b of the transformer 13 is modulated by amplitude shiftkeying (ASK) or by on-off keying (OOK) depending on the transmissionsignal (digital signal) generated by the transmission informationgeneration circuit 110, as will be discussed later.

Note that, although the transmission signal from the transmissioninformation generation circuit 110 is supplied only to the sine wavecontrol signal generation circuit 142 of the sine wave signal generationcircuit 120 in FIGS. 2 and 3, this is not limitative of the presentdisclosure. Alternatively, a switch circuit may be provided in parallelwith the primary winding 13 a of the transformer 13 and the capacitor 14making up the resonance circuit, the switch circuit being controlled tobe turned on and off by the signal from the transmission informationgeneration circuit 110 in synchronization with the control of the sinewave control signal generation circuit 142. As another alternative, aswitch circuit may be provided to address the sine wave signal Ss inputthrough the terminal 103, the switch circuit being controlled to beturned on and off by the signal from the transmission informationgeneration circuit 110 in synchronization with the control of the sinewave control signal generation circuit 142 for ASK modulation or for OOKmodulation.

As a further alternative, the sine wave control signal generationcircuit 142 of the sine wave signal generation circuit 120 may becontinuously held in an operating state in the sine wave mode. Then, theswitch circuit disposed in parallel with the primary winding 13 a of thetransformer 13 and the capacitor 14 making up the resonance circuit, orthe switch circuit provided to address the sine wave signal Ss inputthrough the terminal 103, may be controlled to be turned on and off bythe signal from the transmission information generation circuit 110 forASK modulation or for OOK modulation. Processing operations by therectangular wave signal generation circuit 130 and by the rectangularwave control signal generation circuit 143

The digital signal of information (see FIG. 5) transmitted from thetransmission information generation circuit 110 is supplied as thetransmission signal to the level conversion circuit 131 in therectangular wave signal generation circuit 130. The level conversionsignal 131 outputs a zero level (0 volts) while the input binary signalis being “0” and outputs the high voltage HV (HVr) while the binarysignal is being “1,” thereby generating the rectangular wave signal Sr(see FIG. 5) corresponding to the binary signal. The level conversioncircuit 131 then supplies the generated rectangular wave signal Sr tothe core 11 of the electronic pen 1 via the mode switching circuit 150through the terminal 102.

FIG. 6 is an explanatory diagram explaining the processing operation ofthe rectangular wave control signal generation circuit 143 generatingthe high voltage HVr in the rectangular wave mode. Also, FIG. 7 isanother explanatory diagram further explaining the processing operation.Also in the example of FIG. 6, the switch circuit 121 is configured withan FET, and the selector switch circuit 144 is not illustrated.

In the illustration, the selector switch circuit 122 is in a switchingstate for the rectangular wave mode, with the common terminal c switchedto the switching terminal a to disconnect the parallel connectionbetween the resonance capacitor 14 and the primary winding 13 a of thetransformer 13. That is, the terminal 105 at which the power supplyvoltage VDD is obtained is grounded via a series circuit of the primarywinding 13 a of the transformer 13 and the switch circuit 121 in thiscircuit configuration.

In the rectangular wave mode, the switch circuit 121 is controlled to beturned on and off by a switching signal SWr (see upper portion of FIG.7) from the rectangular wave control signal generation circuit 143. Onthe side of the secondary winding 13 b of the transformer 13, a pulsingvoltage VF depicted in the lower portion of FIG. 7 is obtained. Therectifier circuit 17 rectifies the pulsing voltage VF to generate thehigh voltage HV (=HVr).

The rectangular wave control signal generation circuit 143 monitors thehigh voltage HV (=HVr) received from the rectifier circuit 17 via theterminal 104. In so doing, the rectangular wave control signalgeneration circuit 143 controls the length of the period in which toturn on the switch circuit 121 using the switching signal SWr such thatthe high voltage HV (=HVr) becomes, for example, 20 volts in therectangular wave mode.

As described above, in the rectangular wave mode, the switch circuit 121is controlled to be turned on and off by the switching signal SWr fromthe rectangular wave control signal generation circuit 143 in a mannercausing the rectifier circuit 17 to generate the high voltage HV (=HVr).When the high voltage HV (=HVr) is used as the power supply voltage forthe level conversion circuit 131 in the rectangular wave signalgeneration circuit 130, the rectangular wave signal Sr depicted in FIG.5 is generated. Also, the high voltage HV (=HVr) from the rectifiercircuit 17 is used as the power supply voltage for the mode switchingcircuit 150. This allows the mode switching circuit 150 to output therectangular wave signal Sr without distortion to the terminal 102.

Mode Switching Control by the Control Circuit 140

A flow of mode switching operations performed by the control circuit 140is next described below with reference to the flowchart of FIG. 8.

With this embodiment, the user performs a switching operation beforehandon the slide operation button 32 of the slide operation switch 30 alongthe electronic pen 1 depicted in FIG. 1 in a manner reflecting whetherthe tablet to be used is the sine wave type or the rectangular wavetype.

As described above, the control circuit 140 of the electronic pen 1 inthis embodiment discriminates the mode designation signal SE which isinput via the terminal 109 and which represents the switching state ofthe slide operation switch 30 (S101 in FIG. 8). As a result of thediscrimination, the control circuit 140 determines whether the sine wavemode or the rectangular wave mode is designated (S102).

When determining at S102 that the sine wave mode is designated, thecontrol circuit 140 turns the mode switching signal SW from the modeswitching signal generation circuit 141 into a signal that switches theelectronic pen 1 into the sine wave mode. The mode switching signal SWcauses the mode switching circuit 150 to connect the common terminal Cmwith the sine wave mode terminal Ts, thereby supplying the sine wavecontrol signal generation circuit 142 with a transmission informationsignal causing the sine wave signal Ss to be generated, from thetransmission information generation circuit 110. Also, the modeswitching signal SW causes the selector switch circuit 122 to connectthe common terminal c with the terminal b. This connects the capacitor14 in parallel with the primary winding 13 a of the transformer 13 toconstitute the resonance circuit, and switches the switch circuit 144into the state that selects the side of the sine wave control signalgeneration circuit 142 to activate the oscillation circuit 120R. As aresult, the electronic pen 1 is switched into the sine wave mode andmade ready to operate in that mode (S103).

When determining at S102 that the rectangular wave mode is designated,the control circuit 140 turns the mode switching signal SW from the modeswitching signal generation circuit 141 into a signal that switches theelectronic pen 1 into the rectangular wave mode. The mode switchingsignal SW causes the mode switching circuit 150 to connect the commonterminal Cm with the rectangular wave mode terminal Tr, therebysupplying the level conversion circuit 131 of the rectangular wavesignal generation circuit 130 with a transmission information signalcausing the rectangular wave signal Sr to be generated, from thetransmission information generation circuit 110. Also, the modeswitching signal SW causes the selector switch circuit 122 to connectthe common terminal c with the terminal a. This disconnects the parallelconnection between the primary winding 13 a of the transformer 13 andthe capacitor 14 so as not to constitute the resonance circuit, andswitches the switch circuit 144 into the state of selecting the side ofthe rectangular wave control signal generation circuit 143. As a result,the electronic pen 1 is switched into the rectangular wave mode and madeready to operate in that mode described above (S104).

Following S103 or S104, the control circuit 140 returns control to S101and repeats the subsequent acts.

Example of a Configuration of the Tablet 2S and the Transmission Signalfrom the Electronic Pen 1

Described next is an example of a configuration of the tablet for usewith the electronic pen 1 of this embodiment. The sine wave type tablet2S is taken as an example for the explanation.

FIG. 9 depicts an example of a circuit configuration of key componentsin the sine wave type tablet 2S for use with the electronic pen 1 inthis embodiment. Using the sine wave signal with a frequency of 1.8 MHz,the electronic pen 1 outputs the position detection signal, writingpressure information and side switch information both serving as anexample of important additional information regarding the electronic pen1, and identification information (identifying the electronic pen 1) tothe tablet 2S through the core 11. The tablet 2S includes the positiondetection sensor 21S and the pen indication detection circuit 22S asdepicted in FIG. 9.

The position detection sensor 21S is formed by a first conductor group211, an insulation layer (not illustrated), and a second conductor group212, which are layered from the bottom up. The first conductor group 211has multiple first conductors 211Y₁, 211Y₂, . . . , 211Y_(m) (m is aninteger of at least 1) extending crosswise (X axis direction) andarranged a predetermined distance apart in parallel with each other inthe Y axis direction.

The second conductor group 212 has multiple second conductors 212X₁,212X₂, . . . , 212X_(n) (n is an integer of at least 1) extending in adirection intersecting with the direction in which the first conductors211Y₁, 211Y₂, . . . , 211Y_(m) extend, typically in a lengthwisedirection (Y axis direction) perpendicular to the extending direction ofthe first conductors in this example, and arranged a predetermineddistance apart in parallel with each other in the X axis direction.

In the description that follows, the first conductors 211Y₁, 211Y₂, . .. , 211Y_(m) will be simply referred to as the first conductors 211Ywhere there is no need to distinguish the first conductors from oneanother. Likewise, the second conductors 212X₁, 212X₂, . . . , 212X_(n)will be simply referred to as the second conductors 212X where there isno need to distinguish the second conductors from one another.

A selection circuit 221 serving as an input/output interface isinterposed between a control circuit 220 and the position detectionsensor 21S. Based on a control signal from the control circuit 220, theselection circuit 221 is controlled to select one conductor from thefirst conductor group 211Y and one conductor from the second conductorgroup 212X. Alternatively, the selection circuit 221 may be controlledsimultaneously to select multiple conductors from the first conductorgroup 211Y and multiple conductors from the second conductor group 212X.

The pen indication detection circuit 22S is configured with anamplification circuit 222 connected with the selection circuit 221, aband-pass filter 223, a detection circuit 224, a sample-hold circuit225, an analog-to-digital (AD) conversion circuit 226, and the controlcircuit 220.

A signal from those conductors in the position detection sensor 21S thatare selected by the selection circuit 221 using the control signal fromthe control circuit 220 is input to the pen indication detection circuit22S. In the pen indication detection circuit 22S, the amplificationcircuit 222 amplifies the transmission signal formed by a modulatedsignal of the sine wave signal Ss from the electronic pen 1. The outputof the amplification circuit 222 is supplied to the band-pass filter 223where only the frequency component of the sine wave signal Ss isextracted.

The output signal of the band-pass filter 223 is detected by thedetection circuit 224. The output signal of the detection circuit 224 issupplied to the sample-hold circuit 225 where the signal is sampled andheld at a predetermined timing using a sampling signal from the controlcircuit 220, before being converted to a digital value by the ADconversion circuit 226. The digital data from the AD conversion circuit226 is read and processed by the control circuit 220.

With programs held in an internal ROM, the control circuit 220 operatesto output control signals individually to the sample-hold circuit 225,AD conversion circuit 226, and selection circuit 221. Given the digitaldata from the AD conversion circuit 226, the control circuit 220calculates the coordinates of the position indicated by the electronicpen 1 on the position detection sensor 21S.

In this example, as described above, the electronic pen 1 is configuredto output to the tablet 2S the transmission signal obtained bymodulating the sine wave signal Ss by transmission information includingthe position detection signal from the transmission informationgeneration circuit 110 as well as the writing pressure information andthe side switch information.

The upper portion of FIG. 10 illustrates a typical signal supplied fromthe transmission information generation circuit 110 of the electronicpen 1 to the sine wave control signal generation circuit 142. Asdepicted in FIG. 10, the signal transmitted from the electronic pen 1(sine wave signal Ss) in this example presents a repeat pattern of acontinuous transmission period and a data transmission periodconstituting one cycle. That is, the signal Ss output from theelectronic pen 1 is the sine wave signal continued as a burst signal asdepicted in the middle portion of FIG. 10 during a predeterminedcontinuous transmission period in which the high level of the signalsupplied to the sine wave control signal generation circuit 142 ismaintained as depicted in the upper portion of FIG. 10 (during thecontinuous transmission period in the middle portion of FIG. 10).

The continuous transmission period is set to be long enough for the penindication detection circuit 22S of the tablet 2S to detect the positionindicated by the electronic pen 1 on the position detection sensor 21S.For example, the period is to be long enough for the circuit to scan theentire first conductors 211Y and the entire second conductors 212X atleast once and preferably multiple times.

At the end of the continuous transmission period, the electronic pen 1transmits through the core 11 the transmission data that includes thewriting pressure information in a multiple-bit value (binary code)representing the writing pressure applied to the electronic pen 1, theside switch on-off information regarding the side switch being turned onor off in one bit or multiple bits, and the identification information.

That is, the transmission information generation circuit 110 of theelectronic pen 1 supplies the sine wave control signal generationcircuit 142, depicted in FIG. 3, with a transmission data signal thatgoes High or Low in a predetermined cycle (Td) during the datatransmission period at the end of the continuous transmission period, asillustrated in the upper portion of FIG. 10. The signal controls theoscillation circuit 120R to be turned on and off. As a result, thetransmission signal from the electronic pen 1 becomes the sine wavesignal Ss modulated by amplitude shift keying (ASK) or by on off keying(OOK). That is, as depicted in FIG. 10, ASK modulation or OOK modulationis carried out by performing control such that the sine wave signal isnot output when the transmission data (binary code) is “0” and the sinewave signal is output when the transmission data (binary code) is “1.”

At this time, a first predetermined cycle (Td) following the continuoustransmission period is always High, which is set as a start signal inthe lower portion of FIG. 10. The start signal serves as the timingsignal that allows the control circuit 220 of the pen indicationdetection circuit 22S in the tablet 2S to accurately determine thetiming for subsequent data output. Alternatively, the start signal asthe timing signal may be replaced with a burst sine wave signal duringthe continuous transmission period.

In the pen indication detection circuit 22S of the tablet 2S in FIG. 9,the control circuit 220 detects the position indicated by the electronicpen 1 on the position detection sensor 21S from the signal receivedduring the continuous transmission period. The control circuit 220 thenwaits for the continuous transmission period to end. Upon detecting thestart signal at the end of the continuous transmission period, thecontrol circuit 220 detects data including the writing pressureinformation, the side switch information, and the identificationinformation during the data transmission period, and performs operationsto restore these pieces of data. The control circuit 220 then outputsinformation including the information regarding the detected positionindicated by the electronic pen 1, the writing pressure information, theside switch information, and the identification information to a hostcomputer, for example.

The configuration and the operations of the sine wave type tablet 2Shave been described above in conjunction with the operations of theelectronic pen 1 in the sine wave mode. The configuration and theoperations of the rectangular wave type tablet 2R in FIG. 6 aresubstantially the same as those of the sine wave type tablet 2S and thuswill not be discussed further in detail. That is, the rectangular wavetype tablet 2R has a pen indication detection circuit that detectspen-indicated positions and also detects the writing pressureinformation, the side switch information, the identificationinformation, and the like information.

It is to be noted, however, that the pen indication detection circuit inthe rectangular wave type tablet 2R differs from its counterpart in thesine wave type tablet 2S in that the rectangular wave signal Srtransmitted from the electronic pen 1 is processed. In this case, therectangular wave signal Sr transmitted from the electronic pen 1corresponds to the signal depicted in the upper portion of FIG. 10. Thepen indication detection circuit in the rectangular wave type tablet 2Ris configured to process the rectangular wave signal Sr.

Advantageous Effects of the First Embodiment

The above-described electronic pen 1 is implemented in a manner of beingshared with two different tablets, i.e., the sine wave type tablet 2Sand the rectangular wave type tablet 2R. Also in the electronic pen 1 ofthe above-described first embodiment, the circuits including thetransformer 13 which generates the high voltage signal are configured tobe shared in both the sine wave mode and the rectangular wave mode. Thismakes it possible to simplify the configuration of the electronic pen 1and avoid making the electronic pen 1 larger in size.

Second Embodiment

With the first embodiment above, the user operates the slide operationswitch 30 to switch the electronic pen into either the sine wave mode orthe rectangular wave mode. That means the user needs to know beforehandwhether the tablet is the sine wave type or the rectangular wave type.However, the tablet may not be known to the user as the sine wave typeor the rectangular wave type. It is thus very convenient if the mode ofthe electronic pen is switched automatically depending on the tablettype. A second embodiment of the present disclosure is an electronic penof which the mode is switched automatically depending on the tabletbeing the sine wave type or the rectangular wave type.

FIG. 11 is a schematic diagram explaining an outline of a coordinateinput apparatus formed by an electronic pen 1A and by a sine wave typetablet 2SA and a rectangular wave type tablet 2RA in the secondembodiment of the present disclosure. Those components in FIG. 11 thatare the same as in FIG. 1 are designated by the same referencecharacters.

The electronic pen 1A of the second embodiment is not equipped with theslide operation switch 30 attached to the electronic pen 1 of the firstembodiment, as illustrated in FIG. 11. On the other hand, the sine wavetype tablet 2SA of the second embodiment has a function that outputstype designation information CMs indicating that the tablet is the sinewave type. The rectangular wave type tablet 2RA of the second embodimenthas a function that outputs type designation information CMr indicatingthat the tablet is the rectangular wave type.

The electronic pen 1A of the second embodiment is configured, like theelectronic pen 1 of the first embodiment, to have the sine wave mode inwhich to generate the sine wave signal Ss as the transmission signal andthe rectangular wave mode in which to generate the rectangular wavesignal Sr as the transmission signal, and to switch automaticallybetween the two modes upon receipt of the type designation informationCMs or CMr from the tablet 2SA or 2RA.

In the second embodiment, the tablets 2SA and 2RA, as with the tablets2S and 2R in the first embodiment, have the position detection sensors21S and 21R inside the housings 20S and 20R, respectively. Furthermore,the tablets 2SA and 2RA output the type designation information CMs andCMr via the position detection sensors 21S and 21R, respectively. Thus,in the tablets 2SA and 2RA of the second embodiment, pen indicationdetection circuits 22SA and 22RA are configured to connect with theposition detection sensors 21S and 21R for signal processing,respectively and to provide functions of performing the process ofdetecting positions and the other processes by receiving the sine wavesignal Ss or Sr from the electronic pen 1A and of outputting the typedesignation information CMs and CMr via the position detection sensors21S and 21R, respectively.

In this embodiment, the electronic pen 1A is configured to output thesine wave signal Ss or the rectangular wave signal Sr via the core 11and to receive the type designation information CMs from the tablet 2SAor the type designation information CMr from the tablet 2RA through thecore 11. The electronic pen 1A in the second embodiment is configured toexecute two modes on a time-sharing basis, i.e., a transmission mode inwhich to transmit the sine wave signal Ss or the rectangular wave signalSr, and a reception mode in which to receive the type designationinformation CMs or the type designation information CMr, as will bediscussed later.

Likewise, the tablet 2SA or 2RA is configured to execute two modes bytime sharing, i.e., a transmission mode in which to transmit the typedesignation information CMs or the type designation information CMr, anda reception mode in which to receive the sine wave signal Ss or therectangular wave signal Sr. Under timing control based on the receivedsignal from the tablet 2SA or from the tablet 2RA, the time-sharingprocessing of the electronic pen 1A is synchronized with thetime-sharing processing of the tablet 2SA or 2RA. That is, when theelectronic pen 1A is in the transmission mode, the tablet 2SA or 2RA isin the reception mode; when the electronic pen 1A is in the receptionmode, the tablet 2SA or 2RA is in the transmission mode. When theelectronic pen 1A of the second embodiment is in the transmission mode,either the sine wave mode or the rectangular wave mode is selected.

In the second embodiment, the electronic pen 1A is always in thereception mode when not made ready to receive the signal from theposition detection sensor 21S or 21R of the tablet 2SA or 2RA. When theelectronic pen 1A is brought closer to the tablet 2SA or 2RA and madeready to receive the type designation information CMs or CMr, theelectronic pen 1A discriminates whether the capacitively coupled tabletis the tablet 2SA or the tablet 2RA on the basis of the received typedesignation information CMs or CMr.

The electronic pen 1A then starts time-sharing control of thetransmission period and reception period according to the timing atwhich the type designation information CMs or CMr is received from thetablet 2SA or from the tablet 2RA. When the discriminated type is thesine wave type, the electronic pen 1A enters the sine wave mode togenerate the sine wave signal Ss during the transmission period, andoutputs the generated sine wave signal Ss to the tablet 2SA via the core11. When the discriminated type is the rectangular wave type, theelectronic pen 1A enters the rectangular wave mode to generate therectangular wave signal Sr during the transmission period, and outputsthe generated rectangular wave signal Sr to the tablet 2RA via the core11.

At this time, as discussed above, the tablet 2SA or 2RA is synchronizedwith the time-sharing timing of the electronic pen 1A in thetransmission and reception periods. The tablet 2SA or 2RA during thereception period receives the sine wave signal Ss or the rectangularwave signal Sr reflecting the tablet type, and performs the processes ofdetecting the position indicated by the electronic pen 1A, detecting thewriting pressure information and the identification informationregarding the electronic pen 1A, and handling other additionalinformation.

The electronic pen 1A of the second embodiment is automatically switchedinto the sine wave mode or the rectangular wave mode according to thetype of the tablet 2SA or 2RA. This allows the user of the electronicpen 1A to indicate the position on the tablet 2SA or 2RA without beingaware of whether the tablet is the tablet 2SA or the tablet 2RA, whichis very convenient.

Example of an Electrical Configuration of the Electronic Pen 1A in theSecond Embodiment

FIG. 12 is a block diagram depicting an example of an electricalconfiguration of the electronic pen 1A in the second embodiment. Theelectrical configuration of the electronic pen 1A of the secondembodiment differs from that of the electronic pen 1 of the firstembodiment solely in that the electronic pen 1A automatically enters thesine wave mode or the rectangular wave mode upon receipt of the typedesignation information CMs from the tablet 2SA or the type designationinformation CMr from the tablet 2RA. The remaining features of theelectronic pen 1A are the same as those of the electronic pen 1. Thoseelectrically configured components in FIG. 12 that are the same as thoseof the electronic pen 1 of the first embodiment depicted in FIG. 2 aredesignated by the same reference characters and will not be discussedfurther.

That is, the IC 100 of the second embodiment is not provided with theterminal 109, as depicted in FIG. 12. The second embodiment furtherdiffers from the first embodiment in that the mode switching circuit 150and the mode switching signal generation circuit 141 are replaced with amode switching circuit 150A and a mode switching signal generationcircuit 141A, respectively, and that a received signal processingcircuit 160 is provided.

In the electronic pen 1A of the second embodiment, the core 11 is usednot only to transmit the position detection signal from the electronicpen 1A but also to receive the type designation information CMs or CMrfrom the position detection sensor 21S or 21R of the tablet 2SA or 2RA.

The mode switching circuit 150A is provided with a reception terminal Rin addition to the sine wave mode terminal Ts, the rectangular wave modeterminal Tr, and the common terminal Cm. Given the mode switching signalfrom the mode switching signal generation circuit 141A of a controlcircuit 140A, the mode switching circuit 150A is switched so as toconnect the common terminal Cm with one of the reception terminal R, thesine wave mode terminal Ts, and the rectangular wave mode terminal Tr.That is, when the electronic pen 1A is in the reception mode period, themode switching circuit 150A is switched so as to connect the commonterminal Cm with the reception terminal R. When the electronic pen 1A isin the transmission mode period, the mode switching circuit 150A isswitched so as to connect the common terminal Cm with either the sinewave mode terminal Ts or the rectangular wave mode terminal Tr.

The reception terminal R of the mode switching circuit 150A is connectedwith the input terminal of the received signal processing circuit 160.The received signal processing circuit 160 is made up of an amplifier161 and a received signal discrimination circuit 162. Upon receipt of asignal from the amplifier 161, the received signal discriminationcircuit 162 discriminates whether the received signal is the typedesignation information CMs or the type designation information CMr. Thereceived signal discrimination circuit 162 then supplies the result ofthe discrimination, i.e., whether the received signal is the typedesignation information CMs or the type designation information CMr, tothe mode switching signal generation circuit 141A of the control circuit140A. Also, the received signal discrimination circuit 162 generatesfrom the received signal a timing signal for synchronizing with thetransmission mode period and the reception mode period of the tablet 2SAor 2RA, and supplies the generated timing signal to the mode switchingsignal generation circuit 141A.

Based on the result of the discrimination by the received signaldiscrimination circuit 162, i.e., about whether the received signal isthe type designation information CMs or the type designation informationCMr, the mode switching signal generation circuit 141A determineswhether the transmission mode of the electronic pen 1A is the sine wavemode or the rectangular wave mode. Also, given the timing signal fromthe received signal discrimination circuit 162, the mode switchingsignal generation circuit 141A determines the timing at which to switchbetween the transmission mode period and the reception mode period bytime sharing.

As with the first embodiment, the mode switching signal generationcircuit 141A generates the mode switching signal SW for switchingbetween the sine wave mode and the rectangular wave mode as well as amode switching signal SWA for switching control of the mode switchingcircuit 150A. That is, in the second embodiment, the mode switchingcircuit 150A is switched not by the mode switching signal SW but by themode switching signal SWA.

The mode switching signal SWA causes the mode switching circuit 150A toconnect the common terminal Cm with the reception terminal R during thereception mode period and with either the sine wave mode terminal Ts orthe rectangular wave mode terminal Tr for the determined mode during thetransmission mode period.

The remaining components of the configuration, i.e., the transmissioninformation generation circuit 110, the sine wave signal generationcircuit 120, the rectangular wave signal generation circuit 130, and thecircuits 142, 143 and 144 in the control circuit 140A except for themode switching signal generation circuit 141A, are the same as those ofthe electronic pen 1 in the first embodiment and thus will not bediscussed further.

Mode Switching Control by the Control Circuit 140A

As described above, on the basis of the type designation information CMsreceived from the tablet 2SA or the type designation information CMrfrom the tablet 2RA, the control circuit 140A of the electronic pen 1Ain the second embodiment determines the mode for the electronic pen 1Aand performs transmission/reception mode switching management includingtime-sharing management of the transmission mode and the reception mode.

An example of a flow of the processing operations performed by thecontrol circuit 140A is described with reference to the flowcharts ofFIGS. 13 and 14.

Using the mode switching signal SWA from the mode switching signalgeneration circuit 141A, the control circuit 140A causes the modeswitching circuit 150A to connect the common terminal Cm with thereception terminal R to switch the electronic pen 1A into a mode ofmonitoring the signal received from the tablet 2SA or from the tablet2RA (S111 in FIG. 13). The control circuit 140A then discriminateswhether the signal from the tablet 2SA or from the tablet 2RA isreceived (S112).

When the electronic pen 1A is away from the tablet 2SA or from thetablet 2RA, the electronic pen 1A does not receive the signal from thetablet 2SA or 2RA. Thus, the control circuit 140A in S112 determinesthat no signal is received, returns control to S111, and continues themode of monitoring the signal received from the tablet 2SA or from thetablet 2RA.

The electronic pen 1A, when brought closer to the tablet 2SA or 2RA, maydetermine at S112 that the signal from the tablet 2SA or from the tablet2RA is received. At this point, the control circuit 140A determineswhether either the sine wave type designation information CMs or therectangular wave type designation information CMr is discriminated(S113). When determining at S113 that neither the sine wave typedesignation information CMs nor the rectangular wave type designationinformation CMr is discriminated, the control circuit 140A returnscontrol to S111 and carries out the subsequent acts.

When determining at S113 that either the sine wave type designationinformation CMs or the rectangular wave type designation information CMris discriminated, the control circuit 140A stores (S114) the typedesignation information CMs or CMr as the result of the discriminationinto an internal buffer memory (not illustrated) in the mode switchingsignal generation circuit 141A.

The control circuit 140A then determines to switch to a state where thereception mode and the transmission mode are executed on a time-sharingbasis (S115). Using the mode switching signal SWA from the modeswitching signal generation circuit 141A, the control circuit 140Acauses the mode switching circuit 150A to connect the common terminal Cmwith the reception terminal R to switch the electronic pen 1A into thereception mode (S116).

The control circuit 140A then discriminates whether the signal from thetablet 2SA or from the tablet 2RA is received (S117). When determiningat S117 that the signal from the tablet 2SA or from the tablet 2RA isreceived, the control circuit 140A updates the type designationinformation in the buffer memory with the type designation informationCMs or CMr received and discriminated by the received signaldiscrimination circuit 162 (S118). When determining at S117 that thesignal from the tablet 2SA or from the tablet 2RA is no longer received,the control circuit 140A discriminates whether a received signal missingstate following the disappearance of the received signal is continuedfor at least a predetermined time Ta (S119). Here, the predeterminedtime Ta is set to be longer than a short time period in which theelectronic pen 1A, temporarily separated from the tablet 2SA or from thetablet 2RA, is expected to be again brought closer thereto forcontinuous indication input. Note that the predetermined time Ta mayspan one or multiple reception mode periods.

When determining at S119 that the received signal missing state iscontinued longer than the predetermined time Ta, the control circuit140A returns control to S111, switches to the mode of monitoring thesignal received from the tablet 2SA or from the tablet 2RA, and repeatsthe acts subsequent to S111.

When determining at S119 that the received signal missing state is notcontinued longer than the predetermined time Ta, the control circuit140A returns control to S116 and continues the reception mode. Also,following S118, the control circuit 140A discriminates whether theperiod of the time-sharing reception mode is terminated (S121 in FIG.14). When determining that the time-sharing reception mode period is notyet terminated, the control circuit 140A returns control to S116 andcontinues the reception mode.

When determining at S121 that the time-sharing reception mode isterminated, the control circuit 140A determines to switch the electronicpen 1A into the transmission mode. In accordance with the typedesignation information stored in the buffer memory, the control circuit140A switches the mode switching circuit 150A using the mode switchingsignal SWA from the mode switching signal generation circuit 141A,switches the selector switch circuit 122 using the switching controlsignal SW, and switches the selector switch circuit 144 using the modeswitching signal SW so as to execute the transmission mode (S122).

That is, when the type designation information CMs is stored in thebuffer memory, the electronic pen 1A is in the sine wave mode during thetransmission mode period. The mode switching signal SWA causes the modeswitching circuit 150A to connect the common terminal Cm with the sinewave mode terminal Ts. At the same time, the mode switching signal SWcauses the selector switch circuit 122 to connect the common terminal cwith the switching terminal b. This connects the resonance capacitor 14in parallel with the primary winding 13 a of the transformer 13 toconstitute the resonance circuit. Furthermore, the mode switching signalSW causes the selector switch circuit 144 to be switched into a statewhere the switching signal SWs from the sine wave control signalgeneration circuit 142 is supplied to the switch circuit 121 forexecution of on-off control. This makes the oscillation circuit 120Rready for the oscillation operation.

Thus, in the sine wave mode, the electronic pen 1A is in the state wherethe sine wave signal Ss is obtained on the side of the secondary winding13 b of the transformer 13, as discussed above with reference to FIGS. 3and 4. This is a state in which the sine wave mode signal Ss is suppliedto the core 11 via the terminal 103 of the IC 100 through the modeswitching circuit 150A and the terminal 102. The mode switching circuit150A is supplied with the high voltage HV (=HVs) provided as the powersupply voltage by the rectifier circuit 17 rectifying the sine wavesignal Ss. This allows the sine wave signal Ss to be supplied withoutdistortion to the core 11 through the mode switching circuit 150A.

Also, when the type designation information CMr is stored in the buffermemory, the electronic pen 1A is in the rectangular wave mode during thetiming-sharing transmission mode period. The mode switching signal SWAcauses the mode switching circuit 150A to connect the common terminal Cmwith the rectangular wave mode terminal Tr. At the same time, the modeswitching signal SW causes the selector switch circuit 122 to connectthe common terminal c with the switching terminal a, therebydisconnecting the parallel connection between the resonance capacitor 14and the primary winding 13 a of the transformer 13. Furthermore, themode switching signal SW causes the selector switch circuit 144 to beswitched into a state where the switching signal SWr from therectangular wave control signal generation circuit 143 is supplied tothe switch circuit 121 for execution of on-off control.

Thus, as discussed above with reference to FIGS. 5 to 7, the electronicpen 1A in the rectangular wave mode is in the state where therectangular wave signal Sr from the rectangular wave signal generationcircuit 130 is supplied to the core 11 via the mode switching circuit150A and the terminal 102. The mode switching circuit 150A is suppliedwith the high voltage HV (=HVr) rectified and generated as the powersupply voltage by the rectifier circuit 17 for the secondary winding 13b of the transformer 13. This allows the rectangular wave signal Sr tobe supplied without distortion to the core 11 through the mode switchingcircuit 150A.

Following S122, the control circuit 140A discriminates whether thetransmission mode period is terminated (S123). When determining that thetransmission mode period is not yet terminated, the control circuit 140Areturns control to S122 and continues the transmission mode. Whendetermining at S123 that the transmission mode period is terminated, thecontrol circuit 140 returns control to S116 in FIG. 13, switches theelectronic pen 1A into the reception mode, and repeats the actssubsequent to S116.

Example of a Configuration of the Tablet 2S in the Second Embodiment

Described next is an example of a configuration of the tablet for usewith the electronic pen 1A of the second embodiment. The sine wave typetablet 2SA is taken as an example for the explanation.

FIG. 15 depicts a circuit example of key components in the sine wavetype tablet 2SA used in conjunction with the electronic pen 1A of thesecond embodiment. Of the components in the circuit example in FIG. 15,those that are the same as in the sine wave type tablet 2S of the firstembodiment in FIG. 9 are designated by the same reference characters,and their explanations are omitted hereunder.

As illustrated in FIG. 15, the tablet 2SA includes a selector switchcircuit 23 and a type designation information generation circuit 24 inaddition to the position detection sensor 21S and the pen indicationdetection circuit 22S. The type designation information generationcircuit 24 outputs type designation information CMs indicating that thetablet 2S is of the sine wave type.

The selector switch circuit 23 is switched by a control circuit 220A, tobe discussed later, between the time when the type designationinformation CMs is transmitted and the time when the sine wave signal Ssis received from the electronic pen 1A. A transmission side terminal TXof the selector switch circuit 23 is connected with the output terminalof the type designation information generation circuit 24, and areception side terminal RX of the selector switch circuit 23 isconnected with the amplification circuit 222 in the pen indicationdetection circuit 22S. A common terminal Ct of the selector switchcircuit 23 is connected with the selection circuit 221 serving as aninput/output interface with the position detection sensor 21S.

On the basis of the control signal from the control circuit 220A, theselection circuit 221 is controlled to select one or multiple conductorsfrom the first conductor group 211Y and/or from the second conductorgroup 212X at the time of transmitting the type designation informationCMs. At the time of receiving the sine wave signal Ss from theelectronic pen 1A, the selection circuit 221 is controlled so as toselect one conductor from the first conductor group 211Y and oneconductor from the second conductor group 212X. Alternatively, theselection circuit 221 may be controlled to simultaneously selectmultiple conductors from the first conductor group 211Y and multipleconductors from the second conductor group 212X.

The control circuit 220A, as described above, causes the selector switchcircuit 23 to switch the tablet 2SA between the transmission mode andthe reception mode on a time-sharing basis. In the transmission mode,the control signal from the control circuit 220A causes the selectorswitch circuit 23 to connect the common terminal Ct with thetransmission side terminal TX. This causes the type designationinformation CMs from the type designation information generation circuit24 to be supplied either to one conductor or to multiple conductors viathe selector switch circuit 23 and the selection circuit 221. From theconductors, the type designation information CMs is transmitted to theelectronic pen 1A.

Upon receipt of the type designation information CMs, the electronic pen1A discriminates that the tablet 2SA is of the sine wave type, asdiscussed above. Then, in synchronization with the tablet 2SA switchingbetween the transmission mode and the reception mode, the electronic pen1A switches between the reception mode and the transmission mode asdescribed above. In the transmission mode, the electronic pen 1Atransmits the sine wave signal Ss to the tablet 2SA.

When the electronic pen 1A is in the transmission mode, the controlcircuit 220A of the tablet 2SA is in the reception mode. With the tablet2SA in the reception mode, the control signal from the control circuit220A causes the selector switch circuit 23 to connect the commonterminal Ct with the reception side terminal RX. This allows the sinewave signal Ss sent from the electronic pen 1A to be input to the penindication detection circuit 22S via the switch circuit 23 through thoseconductors in the position detection sensor 21S that are selected by theselection circuit 221. In turn, the pen indication detection circuit 22Sdetects the signal from the electronic pen 1A to determine the positionindicated thereby, as discussed above in connection with the firstembodiment.

In accordance with programs stored in an internal ROM, the controlcircuit 220A outputs control signals individually to the sample-holdcircuit 225, the AD conversion circuit 226, and the selection circuit221, and supplies the switching control signal to the selector switchcircuit 23 causing it to switch between the transmission mode and thereception mode. Also, given digital data from the AD conversion circuit226, the control circuit 220A calculates the coordinates of the positionindicated by the electronic pen 1 on the position detection sensor 21S.

The configuration and the operations of the sine wave type tablet 2SAhave been described above in connection with the operations of theelectronic pen 1A in the sine wave mode. Also, the configuration and theoperations of the pen indication detection circuit 22R in therectangular wave type tablet 2RA are substantially the same as discussedabove. That is, the rectangular wave type tablet 2RA includes theposition detection sensor 21R identical to the position detection sensor21S and a type designation information generation circuit that generatesthe rectangular wave type designation information CMr. Also provided isthe pen indication detection circuit 22R that processes the signalreceived from the electronic pen 1A in the rectangular wave mode toperform position detection and detects the writing pressure information,the side switch information, and the identification information, amongothers.

It has been described above that there are two kinds of tablet typedesignation information, i.e., the type designation information CMsdesignating the sine wave type and the type designation information CMrdesignating the rectangular wave type. Alternatively, either one ofthese two kinds of tablet type designation information alone may beprovided. For example, in the case where the sine wave type tabletoutputs the type designation information CMs but the rectangular wavetype tablet does not output the type designation information, theelectronic pen, when not receiving the type designation information CMs,determines that the tablet is the rectangular wave type. Conversely, therectangular wave type tablet alone may output the type designationinformation CMr.

Advantageous Effects of the Second Embodiment

The electronic pen 1 of the second embodiment discussed above detectsthe type designation information CMs from the tablet 2S or the typedesignation information CMr from the tablet 2R to determine which typeof tablet is now capacitively coupled and ready for position indication,and switches automatically to the mode corresponding to the type of thetablet 2S or 2R. This is very convenient for the user in that there isno need for the user to know the tablet type beforehand.

Third Embodiment

A third embodiment of the present disclosure is a variation of thesecond embodiment. That is, the electronic pen of the third embodiment,to be described below, differs structurally from the above-describedelectronic pen 1A of the second embodiment in terms of the core-sidemember and the related components. The rest of the configuration of theelectronic pen in the third embodiment is the same as that of theelectronic pen 1A in the second embodiment. FIG. 16 depicts an exampleof an electrical configuration of the electronic pen 1B in the thirdembodiment. Of the components in the example of FIG. 16, those that arethe same as in the electronic pen 1A of the second embodiment in FIG. 12are designated by the same reference characters.

In the electronic pen 1A of the above-described second embodiment, theconductive core 11 constitutes the core-side member for exchangingsignals with the tablet 2SA or 2RA. Thus, the electronic pen 1A of thesecond embodiment is switched between the transmission mode and thereception mode on a time-sharing basis, using the core 11 for bothtransmission and reception.

By contrast, the electronic pen 1B of the third embodiment is configuredto have the core-side member formed by a conductive core 11 and aconductive sleeve member 31, as depicted in FIG. 16, so that either theconductive core 11 or the conductive sleeve member 31 is used fortransmission and the other for reception.

Although not illustrated in detail, the sleeve member 31 is attached tothe pen tip of the cylindrical housing of the electronic pen 1B in amanner electrically insulated from the core 11. That is, the sleevemember 31 is a hollow member externally shaped as a truncated cone andhas a ring-like cross-section in a direction perpendicular to the centerline direction (axial direction) of the truncated cone shape. Asdepicted in FIG. 16, the core 11 penetrates through the hollow interiorof the sleeve member 31. A tip 11 a of the core 11 protrudes on the pentip side of the housing of the electronic pen 1B.

In the example of FIG. 16, the core 11 is used solely for transmissionpurposes as with the electronic pen 1 of the first embodiment. Thesleeve member 31 is used to receive the type designation information CMsfrom the tablet 2SA or the type designation information CMr from thetablet 2RA. The type designation information CMs or CMr received by thesleeve member 31 from the tablet 2SA or 2RA is supplied to the receivedsignal processing circuit 160 via a terminal 110 of the IC 100.

Alternatively, the sleeve member 31 may be configured for transmissionand the core 11 for receiving the type designation information CMs orCMr from the tablet 2RA or 2SA.

With the electronic pen 1B of the third embodiment, there is no need toswitch between the transmission mode and the reception mode by timesharing. Thus, a mode switching circuit 150B of the third embodiment isconfigured the same as the mode switching circuit 150 of the electronicpen 1 in the first embodiment. The mode switching circuit 150B isconfigured to omit the reception terminal R and have the common terminalCm connected with either the sine wave mode terminal Ts or therectangular wave mode terminal Tr. Also, in the electronic pen 1B of thethird embodiment, a mode switching signal generation circuit 141B of acontrol circuit 140B generates only the mode switching signal SW as inthe case of the electronic pen 1 of the first embodiment. The modeswitching circuit 150B is switched by the mode switching signal SW.

That is, upon receipt of the signal from the sleeve member 31 via theamplifier 161, the received signal discrimination circuit 162 of thereceived signal processing circuit 160 discriminates whether the typedesignation information CMs from the tablet 2SA or the type designationinformation CMr from the tablet 2RA is received. According to the resultof the discrimination by the received signal discrimination circuit 162,the mode switching signal generation circuit 141B generates the modeswitching signal SW. When the mode switching signal SW causes theelectronic pen 1B to discriminate that the type designation informationCMs is received, the mode switching circuit 150B has the common terminalCm connected with the sine wave mode terminal Ts. When the modeswitching signal SW causes the electronic pen 1B to discriminate thatthe type designation information CMr is received, the mode switchingcircuit 150B has the common terminal Cm connected with the rectangularwave mode terminal Tr. The rest of the configuration is the same as inthe electronic pen 1A of the second embodiment.

With the electronic pen 1B of the third embodiment, there is no need toswitch between the transmission mode and the reception mode on atime-sharing basis. The electronic pen 1B need only perform timingcontrol to output the transmission signal generated by the transmissioninformation generation circuit 110 during the reception mode period ofthe tablet 2S or 2R. This provides an advantage of making modemanagement processing simpler than with the electronic pen 1A of thesecond embodiment.

Fourth Embodiment

In the second and the third embodiments described above, the core-sidemember for receiving the type designation information CMs or CMr fromthe tablet 2SA or 2RA constitutes the input reception circuit thatreceives designation input specifying whether the electronic pen is tooutput the sine wave signal or the rectangular wave signal from thesignal transmission circuit. However, the configuration of the inputreception circuit is not limited to what has been discussed above.

A fourth embodiment of the present disclosure is an example in whichcomponents other than the core-side member make up the input receptioncircuit receiving the type designation information CMs or CMr from thetablet 2SA or 2RA. FIG. 17 depicts a configuration example of keycomponents of an electronic pen 1C, a sine wave type tablet 2SC, and arectangular wave type tablet 2RC in the fourth embodiment.

In the fourth embodiment, the electronic pen 1C exchanges the typedesignation information CMs or CMr with the tablet 2SC or 2RC bywireless communication. The electronic pen 1C is thus provided with awireless communication circuit 41. The tablet 2SC or 2RC is furnishedwith a wireless communication circuit 42 wirelessly communicating withthe wireless communication circuit 41 of the electronic pen 1C.

That is, the electronic pen 1C of the fourth embodiment has the inputreception circuit made up of the wireless communication circuit 41. Thewireless communication circuits 41 and 42 in this embodiment may beconfigured with circuits that perform wireless communication inaccordance with the Bluetooth (registered trademark) standard, forexample. The wireless communication circuits 41 and 42 are not limitedto the above configuration. Also, a wireless communication section isnot limited to radio waves. Alternatively, other wireless communicationsections may be implemented using infrared rays or other kinds of light.

In the fourth embodiment, the wireless communication circuit 42 of thetablet 2SC or 2RC modulates the type designation information CMs or CMrfor conversion into a signal for wireless transmission to the wirelesscommunication circuit 41 of the electronic pen 1C. The wirelesscommunication circuit 41 of the electronic pen 1C demodulates thereceived signal to restore the type designation information CMs or CMr,and supplies the restored information to the received signal processingcircuit 160 via the terminal 110 of the IC 100.

In the electronic pen 1C, as in the above-described electronic pen 1A or1B of the second or the third embodiment, the received signaldiscrimination circuit 162 of the received signal processing circuit 160discriminates whether the received signal is the type designationinformation CMs or the type designation information CMr. Based on theresult of the discrimination, the electronic pen 1C is switched into thesine wave mode or into the rectangular wave mode.

With the fourth embodiment, as described above, when the wirelesscommunication circuits 41 and 42 enter a state where wirelesscommunication therebetween is made available, the electronic pen 1C isautomatically switched into the sine wave mode or into the rectangularwave mode depending on whether the partner of wireless communication isthe tablet 2SC or the tablet 2RC.

Variations of the Second Through the Fourth Embodiments

It has been described above in connection with the second through thefourth embodiments that only the type designation information CMs or CMris transmitted as the transmission signal from the tablet 2SA, 2SB or2SC or from the tablet 2RA, 2RB or 2RC. Alternatively, other signals inaddition to the type designation information CMs or CMr may betransmitted to the electronic pen 1A, 1B or 1C. Such additional signalsmay include information indicative of the start timing of the receptionmode period for the tablet 2SA, 2SB or 2SC or for the tablet 2RA, 2RB or2RC.

Fifth Embodiment

The electronic pen of a fifth embodiment is configured to further reducepower consumption of the primary or the secondary battery constitutingthe power supply circuit 12, compared with the electronic pen 1, 1A, 1Bor 1C of the first, the second, the third, or the fourth embodiment.

The sine wave signal Ss generated by the electronic pen 1, 1A, 1B or 1Cin the sine wave mode of the above-described embodiments has thefrequency defined by the resonance circuit formed by the primary winding13 a of the transformer 13 and by the resonance capacitor 14. Theresonance circuit in this case includes stray capacitance as well. Asdescribed above, the time point at which the switch circuit 121 isswitched to let the oscillation circuit 120R including the resonancecircuit keep generating the sine wave signal Ss is the time point atwhich the voltage of the sine wave signal Ss becomes zero, whichtranslates into very little power loss.

However, the electronic pen 1, 1A, 1B or 1C of the first, the second,the third or the fourth embodiment includes the switch circuit 122switching between two states, i.e., the state where the resonancecapacitor 14 is connected in parallel with the primary winding 13 a ofthe transformer 13, and the state where the parallel connection betweenthe resonance capacitor 14 and the primary winding 13 a of thetransformer 13 is disconnected. The selector switch circuit 122 istypically configured with two transistors. In the sine wave mode, thereoccurs a state where the transistor interposed between the commonterminal c and the switching terminal b of the selector switch circuit122 has on-resistance present. Thus, in the sine wave mode, there occurspower loss due to the on-resistance of the switch circuit 122.

Furthermore, with the electronic pen 1, 1A, 1B or 1C in the rectangularwave mode of the first, the second, the third or the fourth embodiment,the switch circuit 121 is not switched at the time point where thevoltage generated by the transformer 13 reaches zero volts. That meansthere can be significant power loss if there is stray capacitance.

The fifth embodiment is designed to configure an electronic pen thatsolves the above problems and minimizes power loss. FIG. 18 depicts anexample of an electrical configuration of an electronic pen 1D of thefifth embodiment. The example in FIG. 18, as with the example of theelectrical configuration of the electronic pen 1A in the secondembodiment in FIG. 12, is the case where the type designationinformation CMs or CMr from the position detection sensor 21S or 21R ofthe tablet 2SA or 2RA is received via the core 11. Of the components inFIG. 18, those that are the same as in the electronic pen 1A of thesecond embodiment in FIG. 12 are designated by the same referencecharacters, and their detailed explanations are omitted hereunder.

As illustrated in FIG. 18, the electronic pen 1D of the fifth embodimentdoes not include the selector switching circuit 122. The resonancecapacitor 14 is fixedly connected in parallel with the primary winding13 a of the transformer 13. As a result, the terminal 106 of the IC 100is eliminated.

Also, a control circuit 140D of the electronic pen 1D in the fifthembodiment includes a rectangular wave control signal generation circuit143D that differs from the rectangular wave control signal generationcircuit 143 of the above-described second embodiment. The rectangularwave control signal generation circuit 143D is supplied with both thehigh voltage HV (=HVr) output from the rectifier circuit 17 and avoltage VC (=VCr) obtained at the connection point P1 for the primarywinding 13 a of the transformer 13 in the rectangular wave mode. Therest of the configuration is the same as in the electronic pen 1A of thesecond embodiment.

The control operations performed by the mode switching circuit 150A ofthe electronic pen 1D in the fifth embodiment, as well as the processingoperations executed thereby in the reception mode, are identical tothose carried out by the electronic pen 1A of the second embodiment.

When the transmission mode is the sine wave mode, what takes place isthe same as in the electronic pen 1A of the second embodiment. In thiscase, there is no selector switch circuit 122 in the electronic pen 1D,so that the on-resistance stemming from the selector switch circuit 122in the electronic pen 1 of the second embodiment does not exist. Thismakes it possible for the electronic pen 1D of the fifth embodiment inthe sine wave mode to let the oscillation circuit 120R keep oscillatingas a result of the switching executed by the switch circuit 121 at thetime points at which the sine wave voltage VC reaches zero volts. Thesine wave signal Ss is thus generated without power loss, and therectifier circuit 17 provides the high voltage HV (=HVs).

Described below with reference to FIGS. 19 and 20 is an example of aconfiguration of the rectangular wave control signal generation circuit143D in the electronic pen 1D of the fifth embodiment, as well as theoperations performed by the rectangular wave control signal generationcircuit 143D when the transmission mode is the rectangular wave mode. Inthe electronic pen 1D of the fifth embodiment, the resonance capacitor14 is connected in parallel with the primary winding 13 a of thetransformer 13 in the rectangular wave mode as well. As a result, a sinewave-like voltage VCr depicted in the upper portion of FIG. 20 isobtained at the connection point P1 between the primary winding 13 a ofthe transformer 13 and the switch circuit 121.

The rectangular wave control signal generation circuit 143D of theelectronic pen 1D in the fifth embodiment includes a pulse width controlcircuit 1434 in addition to the circuit configuration similar to that ofthe sine wave control signal generation circuit 142 in FIG. 3, theconfiguration being made up of a zero-cross detection circuit 1431, adelay circuit 1432, and a pulse generation circuit 1433. The zero-crossdetection circuit 1431 receives input of the voltage VCr obtained at theconnection point P1. The pulse width control circuit 1434 receives inputof the high voltage HV (=HVr) from the rectifier circuit 17.

The zero-cross detection circuit 1431 and the delay circuit 1432 areconfigured the same as the zero-cross detection circuit 1421 and thedelay circuit 1422 in the sine wave control signal generation circuit142. The pulse generation circuit 1433 generates a switching signal SWrD(see lower portion of FIG. 20) and is configured to produce pulses notwith a fixed pulse width but with a pulse width varied upon receipt of acontrol signal from the pulse width control circuit 1434. In this case,the pulse width of the switching signal SWrD output from the pulsegeneration circuit 1433 is larger than the pulse width of the switchingsignal SWs output from the sine wave control signal generation circuit142.

The switch circuit 121 is turned on during the pulse width period of theswitching signal SWrD from the rectangular wave control signalgeneration circuit 143D and is turned off during the other periods. Thepulse width control circuit 1434 performs on-time control of the switchcircuit 121 in a manner adjusting the pulse width of the switchingsignal SWrD from the pulse generation circuit 1433 such that the highvoltage HV will become the high voltage HVr in the rectangular wavemode.

That is, as illustrated in FIG. 20, in the electronic pen 1D in therectangular wave mode of the fifth embodiment, the switching signal SWrDfrom the rectangular wave control signal generation circuit 143Dpresents a pulse width period delayed by the delay time DL of ¼ of onecycle T of the sine wave signal Ss in the sine wave mode from thezero-cross point Zc2 of the sine wave voltage VCr obtained at theconnection point P1, as illustrated in FIG. 20. Thus, the switch circuit121 is turned on at time points where the sine wave voltage VCr becomeszero volts.

However, in the rectangular wave mode, the pulse width period of theswitching signal SWrD is longer than that of the switching signal SWs inthe sine wave mode. That means zero volts continue over the pulse widthperiod of the switching signal SWrD. As a result, the sine wave-likevoltage VCr presents a deformed sine waveform as depicted in the upperportion of FIG. 20.

When the switch circuit 121 is turned off at the end of the pule widthperiod of the switching signal SWrD, the sine wave-like voltage VCrbecomes larger in amplitude than the sine wave voltage VC in the sinewave mode by as much as a portion corresponding to the pulse widthperiod of the switching signal SWrD. That is, the sine wave-like voltageVCr becomes higher than the voltage 2VDD by the shaded portion in theupper portion of FIG. 20. Thus, the sine wave-like voltage VCr of thelarge amplitude waveform is boosted in keeping with the turn ratio ofthe primary winding 13 a to the secondary winding 13 b in thetransformer 13, the sine wave-like voltage VCr being further rectifiedby the rectifier circuit 17. This generates in the rectangular wave modethe high voltage HV (=HVr) that is higher than the high voltage HV(=HVs) in the sine wave mode.

The high voltage HV thus generated is supplied to the pulse widthcontrol circuit 1434 in the rectangular wave control signal generationcircuit 143D as described above. The pulse width control circuit 1434 inthe rectangular wave control signal generation circuit 143D controls thepulse width period of the switching signal SWrD in such a manner thatthe input high voltage HV becomes the high voltage HVr in therectangular wave mode. This controls the on-period length of the switchcircuit 121 illustrated in the lower portion of FIG. 20. Accordingly, asize (area) of the shaded portion of the sine wave-like voltage VCr inthe upper portion of FIG. 20 is controlled. As a result, the highvoltage HV output from the rectifier circuit 17 is controlled to becomethe high voltage HVr in the rectangular wave mode.

Because the selector switch circuit 122 does not exist in the electronicpen 1D of the fifth embodiment, there is no power loss stemming from theon-resistance of the selector switch circuit 122, which furthercontributes to reducing power consumption.

Also in the rectangular wave mode, the electronic pen 1D of the fifthembodiment has the switch circuit 121 switched at the timing at whichthe sine wave-like voltage VCr becomes zero volts. This substantiallyeliminates power loss. As a result, the electronic pen 1D of the fifthembodiment minimizes power consumption of the primary battery or thesecondary battery of the power supply circuit 12, thereby prolongingbattery life.

In the electronic pen 1D of the fifth embodiment depicted in FIG. 18,the sine wave control signal generation circuit 142 and the rectangularwave control signal generation circuit 143D are separately provided.However, as is evident from the foregoing description, the zero-crossdetection circuit 1421 may double as the zero-cross detection circuit1431 or vice versa and the delay circuit 1422 may double as the delaycircuit 1432 or vice versa in the sine wave control signal generationcircuit 142 and in the rectangular wave control signal generationcircuit 143D. Thus, in the fifth embodiment, the sine wave controlsignal generation circuit 142 and the rectangular wave control signalgeneration circuit 143D may be configured to share the zero-crossdetection circuit and the delay circuit. This arrangement furthersimplifies the circuit configuration.

OTHER EMBODIMENTS OR VARIATIONS

In the above embodiments, it has been described that the IC-based signalprocessing circuit of the electronic pen has the mode switching circuits150, 150A, 150B, 150C, and 150D included in the IC 100. Alternatively,the mode switching circuits 150, 150A, 150B, 150C, and 150D may beprovided as external components of the IC 100. Also, in the aboveembodiments, it has been also described that most of the components ofthe signal processing circuit in the electronic pen are provided in ICform. Obviously, however, these components may alternatively be providedas discrete components making up electronic circuits.

Also, in the above embodiments, it has been also described that the sinewave signal generation circuit 120 is configured as an externallyexcited oscillation circuit. However, the present disclosure is notlimited to this configuration. Also, the configuration of the rectifiercircuit 17 is obviously not limited to what has been described in theconfigurations of the above embodiments.

Also, in the above embodiments, it has been described that the waveformof the first signal is the sine waveform and the waveform of the secondsignal is the rectangular waveform. However, the waveform of the secondsignal is not limited to the rectangular waveform and may be some otherwaveform such as a triangular waveform. The waveform of the first signalis also not limited to the sine waveform and may be some other waveform.

In the above embodiments, it has been also described that the signalfrom the transmission information generation circuit 110 controls thesine wave control signal generation circuit 142 in a manner convertingthe sine wave signal into an ASK-modulated signal or an OOK-modulatedsignal using the transmission information. However, the presentdisclosure is not limited to this configuration. Alternatively, thetransmission information generation circuit 110 may not control the sinewave control signal generation circuit 142. Instead, a modulationcircuit (for ASK or OOK modulation) may be provided to address the sinewave signal obtained as a continuous wave signal on the side of thesecondary winding 13 b of the transformer 13. The transmissioninformation may then be supplied to this modulation circuit to obtainthe ASK-modulated or OOK-modulated signal thereby.

It is to be noted that the embodiment of the present disclosure is notlimited to the foregoing embodiment, and that various changes can bemade without departing from the spirit of the present disclosure.

What is claimed is:
 1. An electronic pen comprising: a conductive corebody; a power supply circuit; a first signal generation circuit which,in operation, receives power from the power supply circuit and generatesa first signal; a second signal generation circuit which, in operation,receives power from the power supply circuit and generates a secondsignal different from the first signal; and an operation switch which,in operation, sets an operation mode of the electronic pen to either afirst operation mode or a second operation mode, wherein, while theoperation mode of the electronic pen is set to the first operation mode,the conductive core body transmits the first signal generated by thefirst signal generation circuit, and wherein, while the operation modeof the electronic pen is set to the second operation mode, theconductive core body transmits the second signal generated by the secondsignal generation circuit.
 2. The electronic pen according to claim 1,further comprising: a control circuit which, in operation, controlswhether the first signal or the second signal is supplied to theconductive core body based on an operation of the operation switch. 3.The electronic pen according to claim 1, wherein an amplitude of thefirst signal is different from an amplitude of the second signal, orwherein a frequency of the first signal is different from a frequency ofthe second signal.
 4. The electronic pen according to claim 1, whereinthe first signal and the second signal are modulated according totransmission information.
 5. The electronic pen according to claim 4,wherein the transmission information is writing pressure information. 6.The electronic pen according to claim 4, wherein the transmissioninformation identifies the electronic pen.
 7. The electronic penaccording to claim 1, wherein a waveform type of the first signal isdifferent from a waveform type of the second signal.
 8. The electronicpen according to claim 7, wherein the waveform type of the first signalis a sine wave, and wherein the waveform type of the second signal is arectangular wave.
 9. The electronic pen according to claim 1, whereinthe first signal is configured to be used by a first type of tablet, andwherein the second signal is configured to be used by a second type oftablet that is different from the first type of tablet.
 10. Theelectronic pen according to claim 9, wherein the first signal isconfigured to enable the first type of tablet to detect a positionindicated by the electronic pen, and wherein the second signal isconfigured to enable the second type of tablet to detect the positionindicated by the electronic pen.
 11. The electronic pen according toclaim 1, further comprising: a mode switching signal generation circuitwhich, in operation, generates a mode switching signal that causes thefirst signal generated by the first signal generation circuit to beprovided to the conductive core body while the operation mode of theelectronic pen is set to the first operation mode, and causes the secondsignal generated by the second signal generation circuit to be providedto the conductive core body while the operation mode of the electronicpen is set to the second operation mode.